TW200810920A - Multilayer sealant film - Google Patents

Abstract

A multilayer film suitable for sealing containers such as used for food packaging, and methods of making the film, are described. The film is particularly suitable for sealing containers made from polylactic acid (PLA). The multilayer film includes (a) a substrate that includes a polymeric base layer; and (b) on the substrate, a heatseal layer containing a PLA homopolymer or copolymer. The heatseal layer further includes dispersed therein an adhesion promoter, or alternatively the substrate further includes the adhesion promoter in a layer on a surface of the polymeric base layer between and adjacent the base layer and the heatseal layer. An antifog agent may also be included in the heatseal layer or on the surface of the heatseal layer opposite the substrate.

Description

200810920 ~ ~ ^ j--- IX. Description of the Invention: [Technical Field] The present invention relates to a method of manufacturing a multilayer film and in particular to a multilayer sealant film Manufacturing method. [Prior Art]

♦ Polylactic acid (PL A ) is a highly biodegradable polymer that can be derived from natural sources such as corn. The use of PLA for the manufacture of food packaging trays is gaining popularity, at least in part, due to the ease of biodegradability of PLA and the extremely high oxygen permeability and moisture permeability of discs made from pLA, and therefore PLA is well suited for packaging fresh products. . However, from PLA, discs tend to soften and deform at temperatures as low as 1 〇 4 ° F (40 Å). Due to this disadvantage, the cover resin used for the PLA disk must be heat-sealed at a low temperature TM temperature: sealing: the conventional sealing film is not sufficiently low: although * there;; ==: degree The layer is accompanied by = but these shells are used for commercial use, and the seams required for commercial use are beneficial. In addition, the invention can provide a multilayer film, which includes a multilayer film, which includes

200810920 a) a substrate comprising a polymeric matrix layer; and further comprising: ====== the heat sealing layer further comprises adhesion promoting;; the layer sealing of the base layer of the sand layer of the f layer: = = providing a The multi-layer film just described on the film side of the closed cell of the open container is loaded with heat sealing = Γ, and the present invention provides a method of producing a multilayer film. Mj: 7 coating liquid onto a substrate comprising a polymeric substrate, the coating liquid or substrate is further included in the layer on the surface of the polymeric substrate layer;;: the coating agent is applied to the liquid; and b) is removed The solvent is used to form a heat seal layer comprising a pLA polymer. Further, the present invention provides a coating composition comprising a pLA polymer, an I polyester, and a solvent. [Embodiment] The present inventors have found that it is very difficult to suitably adhere a pLA polymer to pdyeihylene terephthalate (PET) and various other substrates using a conventional method. To solve this and other problems, the multilayer film of the present invention comprises a substrate comprising a polymeric matrix layer and a heat seal layer comprising a PLA polymer on the substrate. One or both of the heat seal layer and the substrate further comprise an increase in the pLA polymer and the polymerizable group 200810920 2, the footing agent, while maintaining a good low temperature heat sealing the second milk 2::: Explain 'other terms used herein "PLA polymer,," (4), and a repeating monopolar copolymer comprising at least 3 G mol% of lactic acid. If the substrate comprises an adhesion promoter in the form of a layer, the layer is formed on the layer or formed in a polymeric matrix layer. (: outside the production line). - In general, the polymerization of the heat-sealing layer, ie, the heat-sealable polymer, should have a specific polymerization; =5 yesterday's usually at least _, and usually lower A thermoplastic polymer having a two-person/dish degree. The softening point is preferably higher than 75. If the adhesion promoter is dispersed in the heat-sealing layer, the dispersion may be in the form of a homogeneous solution, or the layer may contain a dispersion polymerization. Phase and difference

Compound phase. In some implementations, the adhesion promoter constitutes ^. 50 wt% of one of the phases, and the pLA polymer constitutes another phase of the phase that exceeds the private enthalpy. The adhesion promoter may be dispersed in the PLA polymerization, or the PLA polymer may be dispersed in the adhesion promoter. The appearance of a haze in the heat seal layer of some of the embodiments of the present invention indicates the presence of a different composition, polymer phase. An exemplary formulation that provides the appearance and good sealing performance after drying on a substrate consists of 30% amorphous pLA polymer (pLA _0D, from Minnetonka, face ureW〇rks LLC, D, L-poly Lactic acid polymer) and 70% copolyester (sebacic acid/terephthalic acid/ethylene glycol '45/55/100 molar equivalent). The present inventors have found that by carefully selecting an adhesion promoter, it is possible to produce a multilayer which can seal a good adhesion between a PLA polymer layer and a substrate at a temperature sufficiently low that =LA does not deform at a sufficiently low temperature. Thin 200810920 1 ι^ιχ; Thin =:::=::=: Combined substrate layer This invention can use multilayer films of any thickness. The thickness can be in the range of 12 μm. The thickness of the heat seal layer is in the range of 0: 5 to 20 microns, more usually in the range of 2 Å to 1 〇 in the opposite direction. The heat seal layer can usually be produced by solution coating, and is applied by ^, extrusion coating or co-coating. Other methods of cloth may be difficult to achieve

The disadvantage of the two PLA polymer is that the polymer is pre-dried to be a second solution. This additional step can be omitted when the PLA polymer is applied by solution coating at a typical condition P' below the alloying temperature of the PLA polymer. If PLA: 乂^ has a separate adhesion promoting layer, then the thickness of the upper layer between the upper layer and the upper layer is usually in the right heat seal layer including the adhesion or dispersing in the towel (4), then the viscosity The amount of promoter is typically at least 1 wt〇/〇, more typically at least 10 wt%, and most typically at least 2〇= or even at least 3 G Wt°/, to promote the combined weight of the pLA polymer. . The amount is usually at most 9 Qwt%, more preferably 70 wt/〇, and most usually at most. In those embodiments of the invention where the heat seal layer is relatively transparent (not obscured), the adhesion, the relative amount of the sword relative to the PLA polymer, may be suitably somewhat lower. For example, the amount of the 3' gastric adhesion promoter can generally be at least 20 wt%, more typically at least 3 mechanical %, and most typically about the weight of the combination of the accelerator and the pLA polymer. 40 wt%. The amount is typically up to 6 〇%, more typically up to 5 〇 wt/〇. In the case where it is desired to prevent the formation of water droplets on the surface of the film (when used in the context of promoting the use of the 200810920 JL jjAj^ environment, such as packaging of the product), the antifogging agent is further described below. The composition of the type of film will now be discussed in detail, followed by a description of how the film is made and the film, and the sealing layer comprises at least pla polymer. The t-port type PLA polymer used in accordance with the present invention may be any of the species known in the art and may include a Wei homopolymer as well as a copolymer. Suitable comonomers include hydrazine; 2H〇C(R)(R2)(CH2)nC〇〇H of these comonomers, wherein R and each of the ruthenium are H or a substituted or unsubstituted CrC5 group Group, and n is an integer from 〇 to 10. The PLA polymer may be amorphous (i.e., at least 90% amorphous by scanning calorimetry), or it may be crystalline and crystalline. Typically, the PLA polymer will crystallize up to 50%, and more typically up to t 2% by weight. The PLA polymer may be a lactic acid homopolymer, which may be one or more of the following different polymers: D_polylactic acid, L-polylactic acid, D, L·polylactic acid, and mesopolylactic acid. . Polylactic acid and [_ polylactic acid are polymers of 10 $ ship enantiomers and are optically active polymers. D, L· Polylactic acid is prepared from racemic t acid, i.e., a copolymer of D_polylactic acid and L-polylactic acid having a defined D_polylactic acid and L-polylactic acid unit configuration. The meso-polylactic acid is a mono-concentration of D-lactic acid and a random lactic acid copolymer. The morphology of the pLA homopolymer is known to be controlled by the ratio of the D isomer to the L isomer in the polymer backbone. Generally, the higher the D-lactic acid content, the less the polymer crystallizes. Any known polymerization method (such as polycondensation and ring opening polymerization) can be employed. -10- 200810920 Polymeric lactic acid can be used. For example, in the polycondensation process, a mixture of L-lactic acid, D-lactic acid or such lactic acid is directly subjected to a dehydration polycondensation reaction by means known in the art. In the ring-opening polymerization method, a crosslinking reaction (i.e., a cyclic dimer of lactic acid) is subjected to a polymerization reaction in the presence of a catalyst. Lactide can be a dimer of L lactic acid, a dimer of D-lactic acid or a mixed dimer of L_lactic acid and D_lactic acid. The isomers may be mixed and polymerized to obtain a polylactic acid having any desired composition and crystallinity. A small amount of a chain extender such as a diisocyanate compound, an epoxide or an acid anhydride may be used to increase the molecular weight of the PLA polymer. While the polymer may be in any molecular weight range, typically the weight average molecular weight should be in the range of 60,000 to 1,000,000 Daltons. Generally, if the molecular weight is less than 6 〇 000, appropriate physical properties may not be obtained. On the other hand, if the molecular weight is more than 1,000,000, the melt viscosity may be extremely high, resulting in poor formability. The PLA polymer can also be a copolymer of lactic acid and one or more comonomers. If comonomer is present, the comonomer collectively constitutes less than 5 〇 〇 m 〇 1% 'typically less than 30 mol %, and more typically less than 1 〇 1% of the PLA polymer. Examples of the comonomer include: caprolactone; hydroxycarboxylic acid, such as glycolic acid, 3-hydroxybutyric acid, 'hydroxybutyric acid, 4-hydroxyvaleric acid, and & dadsonic acid, polyol, Such as ethylene glycol, propylene glycol, butanediol, • neopentyl alcohol, poly(ethylene glycol), glycerol and pentaerythritol; and multiple sufficiency, such as succinic acid, adipic acid, azelaic acid, anti- Butyric acid, terephthalic acid, isophthalic acid, 2,6-naphthalenediic acid, 5-sodium sulfoisophthalic acid, and 5-tetrabutyl feldsparin 200810920 - lf〇is〇phthalate) 0 is present) preferably H t '"" biodegradable comonomer (if some embodiments are eliminated, the film comprises an anti-fogging agent to reduce or seal The surface of the ruthenium helps the surface to form fog. The antifogging agent can be dispersed (4) the portion of the smear-like substance is dispersed in the heat-sealing layer, or it can be floated to the surface.

Pti can be applied directly to the surface of the heat seal layer by dipping, spraying or otherwise coating from a suitable solvent. Examples of suitable antifogging agents include alkaneized fat mash, such as atme 502; sorbitan vinegar II = R® 103, other known nonionic, anionic and cationic surface f-types, such as polyoxyalkylene fatty acids Ester, alkoxylation assay, mixing ί:, di- or triglyceride, fatty acid esters of polyhydric alcohols, other polyalkoxyides and the like. ATMER8 products are derived from τ__η, stomach

Specialty Chemicals C〇rp·. If the antifogging agent is included in the heat seal layer, the aerosol will typically constitute about (U wt% to about 15 Å of the heat seal layer, more typically from about 0.5 * % to about 1 G wt %. If directly applied to the heat seal layer The heat flux is in the range of from about Q1 to about 5 wt/o, and is generally in the range of from about Q. 1 wt% to about _%. The layer may comprise inorganic particles such as cerium oxide and/or a slip additive such as a wax and/or polytetrafluoroethylene dispersion. Antioxidants may also be included in certain applications. In certain embodiments, the heat seal layer Can be free of plasticizers (such as polyglycols or polyethers, or the § of these polymers), tackifiers and / or inorganic · 12-200810920 fillers. In some implementations, _ outside the aliphatic (3) $ does not contain PLA polymer adhesion promotion _, as used herein, in the term "adhesion promoter" in the PLA polymer or used as a heat to heat seal interlayer, according to the test method of the example a material having a heat-sealing strength between the base layers of the base layer. Usually 1 can provide at least 200 吋, and more usually at least 400 gram / ^. 300 g / separation film when 'heat seal layer is still good with each H, in the case of heat seal layer (10) according to method (ii), and the separation formula is suitable. Adhesive accelerator includes (but not, cohesive failure mode EVA) (ethylene vinyl acetate) and _: : ) ene copolymers, such as and tackifier resins, such as rosin tree terpene - decyl acrylate;

In certain embodiments, the term "copolymerization" as used in the context of adhesion promotion means derived from at least = (tetra) lipids, as in this species, aromatic two ships and at least _ (and preferably only - acid or low carbon filaments thereof). (ie, up to 14 carbon atoms = diol.) The purpose of forming a private carboxylic acid, including stupid acid, by a method of shrinking at a temperature of about 275. Desalination of diterpenic acid. Demonstration: lipids such as succinic acid, indole, adipic acid, hydrazine 1:==acid: preferably azelaic acid, adipic acid and azelaic acid, and more佳为:::了' -13- 200810920 (such as ϊ ΐϊϋ ' ' poly s s intended to contain no more than 9g% of aromatic diacidic acid in the polyester total: acid: less than 1% by weight of aliphatic dicarboxylic acid, percentage The concentration is at least 55. Usually, the copolymerization of aromatic Weiwei can be 6G Moire and 6G Moore% or more. Generally speaking, the concentration of the aromatic second ship is the most suitable for XI, ear and More typically no more than 70% by mole, and see, copolymerization. The concentration of the second ship in the copolymerized vinegar is more usually at least 3, usually at least 2% by mole, and the percentage is = ^ usually up to 45 mol%. When at least 5 wt% of the aromatic diacid- ιτΪί diol is present, including aliphatic diols such as alkane diols. The diols such as ethylene glycol 'diethylene glycol di b4 are known as 1,3-butanediol, 丨 丁 曰 曰 ( ( (ie, by differential scanning calorimetry at least 9 () % = = as previously indicated, the copolyester can be combined with the PLA poly-palladium: rr, that is, the polymer layer can be included in the poly-synthesis layer, and any layer known in the art can be included.瞑Polymerization-14- 200810920, the restriction condition is _ strong made by the open material. Lai is mechanically more than only the PLA homopolymerized (Nylon) film, used; B: 2:: limited) polyester film In some embodiments, the polymeric matrix layer comprises linear polyester 2. t ^ ΐ linear poly (4) 'linear poly cool usually has about 0.5 membrane degree' Usually about G.6 characteristic viscosity.

Heart '雔:& axis oriented polyethylene terephthalate §| (PET) film, biaxially oriented poly(ethylene) phthalate (1) naphthalate, PEN film. Particularly suitable are biaxially oriented and thermosetting polyethylene terephthalate. Such materials are well known in the art and are described, for example, in the awarding of ^

Stokes, U.S. Patent No. 7,375, (incorporated herein by the name of the bow). The preparation of water to benzoic acid ethylene glycol polymer is well known to those skilled in the art and is disclosed in various articles, such as Encydapedia Qf.

Polymer Science and Engineering, 2nd Edition, Volume 12, wiley, Ν·Υ· ‘pp. 1-133. The polymer is usually obtained by condensing a suitable dicarboxylic acid or a lower alkyl diester thereof with ethylene glycol. Polyethylene terephthalate is formed from terephthalic acid or an ester thereof, and polyethylene naphthalate is formed from 26-naphthalenedicarboxylic acid or an ester thereof. In the case where a co-extruded double-layer polyester/co-vinegar film is used as a substrate on which a PLA polymer is coated, a double-layer film composite is conveniently manufactured by a method including the following steps: multiple extrusion through a porous mold The layer of -15-200810920 is pressed or coextruded (for example, as described in U.S. Patent No. 3, δ 71,947), followed by molecular orientation and thermal curing by stretching in two or more directions. Convenient method and device description for co-compression (referred to as single-channel co-pulling) • U.S. Patent No. 4,165,21 and British Patent Specification No. 1,115,007. The method comprises simultaneously extruding a first- and a first-poly condensate stream from two different extruders, causing the two streams to be in a body-body in a tube leading to a manifold of the extrusion die and in a streamlined flow condition The two (4) intentions are reduced by the mold, so that the two kinds of polyesters occupy different flow regions without mixing, thereby producing a film composite. The biaxial orientation of the poly(p-diethyl phthalate) moiety of the film composite can be accomplished by stretching the composite in two directions perpendicular to each other, usually at a temperature of from about 78 t to about 10,000 Å. In general, the conditions used for stretching the composite may be used to partially crystallize the first thermal bonding layer, and in both cases, preferably at a size limit, higher than the crystalline melt solubility of the first thermal bonding layer but low The composite is thermally cured at a temperature at the crystallization temperature of the polyethylene terephthalate. The composite is then allowed to cool or the composite is caused to: cause the first thermal bond layer to be substantially amorphous, while in the attached portion; leaving a high degree of crystallinity. Therefore, it is preferred to carry out the stretching operation generally after 15 to 25 (the range of TC) after heat curing under the size limitation. A convenient method for stretching and thermal curing is described in U.S. Patent No. 3,107,139. The coextruded film composite of the type described herein incorporated into the polyester matrix layer (the copolymerized vinegar layer on the substrate layer) may be by DuP〇nt Tdjin Fiims '吋

Wilmington, DE under the name MELINEX® 301H Market. As described above, the films may be coated with the PLA polymer of the present invention. In the -16-200810920, : ester coating formulation, with or without other copolymerizations, the multilayer film of the present invention may be used by using pla The solution coating in a solvent also contains the term "solvent," meaning a volatile carrier such as - or both, and the resulting mixed U promotes Or other dispersions, and in the strict sense can also be straight, 1 = /, microemulsion pure (but not limited to) water, four traces: two: suitable solvent when water is used as a solvent, emulsifier It can be used to make an emulsion, etc. It has an adhesion promoter. For example, 4 is required to be laminated on two layers of the substrate. However, two: (2) (a polyester film of a common polyester layer. In each case) It can be applied to the substrate to provide a multilayer film. The coating can be subsequently applied by any of the techniques known in the art to reduce the metering and gravure coating. The present inventor. Now package ί • Using a solution coating method to prepare a method having a relatively thin heat '^20«} (such as extrusion or co-extrusion coating) 庐 ^ " from /, into a composite film made of other materials such as lamination or extrusion coating; : 冓 冓 冓 某些 某些 某些 某些 某些 某些 某些 某些 某些 某些 某些 某些 某些 某些 某些 某些 某些 某些 某些 某些 某些 某些 某些 某些 某些 某些 某些 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 A singular 'for example, a PLA disk. Usually, although it is made of a disk or a complex polymer', it is also possible to use lactic acid and ugly according to the invention (including but not limited to those used in the heat seal layer above). Filaments of PLA-human = mentioned 彳 躲 ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ The film is sealed on the side of the film. &, in the sample sample test g, the following test method is used in the subsequent examples. (i) Measuring the heat-sealing strength of the disk, such as 2 在 at 35 psi吋 厌 ^ ^ — on the heat sealing machine in the cut out of the loose seal _ and the belt of the belt (25 milkwood state to 0.25 8 feet per minute M + a- /, so Instron's required negative head speed measurement pulls the seal apart and smashes it together and under the pressure of 35 psi to lower the heat seal layer of the two film samples, 'the heat seal strength of the own. The sealing film "to the point of view per minute" is determined by the linear force of the inner width seal of the inner measuring strip, and the fixed speed peeling force of 0.25 meters in the strip is used to determine the heat seal strength.

Ul) can be used to measure the percentage of crystallinity by differential scanning calorimetry. At -18- 200810920

A 5 gram sample taken from the film was self-twisted at 80 ° C/min on a Perkin Elmer DSC7B differential scanning calorimeter. Heat to 300 ° C. The degree of crystallinity present in all samples can be derived from the percentage of crystallinity. Sample Preparation Preparation of Coating Solution #1: 99 grams of PLA 4060D (low crystallinity) was purchased from NatureWorks LLC of Minnetonka, MN.

Polylactic acid polymer), 0.5 g of KEMAMIDE E anti-caking agent (available from Witco), and 8 丫B 01〇244 slip agent (available from 111.0 coffee 6) were added to 500 g of tetrahydrofuran (THF). The mixture was stirred for 30 minutes to prepare a coating solution #1. Preparation of Coating Solution #2: 69 grams of PLA4060D, 30 grams of azelaic acid/terephthalic acid/ethylene glycol (45/55/100 mole equivalent) of copolyester, 〇·5 grams of KEMAMIDE E and 〇·5 g SYL0ID 244 was added to 400 g THF. The mixture was stirred for 3 minutes to prepare a coating solution #2 〇4 Sample 1: Coating solution #1 was applied to a %-type MYLAR E film by a forward roll coating method (biaxially oriented polyethylene terephthalate) Vinegar film, made by DuPont Teijin Films) ±. The roll gap was adjusted to achieve a dry coating weight of 8 gram per square meter. Dry the wet paint for 1 minute at 1 (Κ) ΐτ. The sample was coated by a forward roll coating method on a MYLAR® hidden film (a biaxially oriented polyparaphenylene phthalate film, which was made of DuP_Tei fine FUms). . Adjust to achieve a dry coating weight of 8 g/m2 Dry wet paint for 1 minute. #卜 -19- 200810920 Sample 3: Coating solution #2 was applied to a Type 92 MYLAR E film made of DuPont Teijin Films by a forward roll coating method. The roll gap was adjusted to achieve a dry coating weight of 8 grams per square meter. Dry the wet paint for 1 minute under 丨(9). Sample 4: The coating solution was magically applied to a MYLAR 1〇〇〇L film made by DuPont Teijin Films by a forward roll coating method. Adjust the roll gap to achieve a dry coating weight of 8 g/m2. Dry the wet paint for 1 minute. u ^ The heat-prepared f-film of Sample M was heat-sealed to the raw material of the PLA disk and itself according to the above method (1) and W. The results of the obtained heat seal strength are shown in the following table in grams per gram. ',,,

* Start sealing by hand before the sample is peeled off by Instron. = Comparison of 2 and 2 indicates that the heat seal containing only pLA has a better heat seal on the base film of the second layer (sample 2) than at .p H). In addition, comparing the mouths 1 and 3, it can be seen that in the absence of the intermediate copolymerization layer, the heat seal strength of the water is increased from that of the rut-to-PLA heat seal layer (sample 3). Finally, compare the ^^ mouth layer (the sample can be seen in the copolymerization _ and the common product 3' life is better than the individual - alone. /, _ as the intermediate layer production -20- 200810920, although reference has been made herein to specific implementations The invention is not limited to the detailed description of the invention, and may be made in the detailed description without departing from the scope of the invention. Change. [Simple description of the diagram] No [Main component symbol description]

Claims (1)

200810920 ---- X. Patent application scope: 1. A multilayer film comprising a) a substrate comprising a polymeric matrix layer; and b) a heat sealing layer comprising a PLA polymer on the substrate; The sealing layer further comprises an adhesion promoter dispersed in the towel, wherein the substrate is on the surface of the polymeric substrate layer of the polymeric substrate layer and the polymeric substrate layer of the heat sealing layer The layer is covered with an adhesion promoter. The multilayer film according to Item 1, wherein the base layer comprises polyethylene terephthalate. 3. The multilayer film of claim i, wherein the substrate comprises the adhesion promoter layer, and wherein the adhesion promoter layer comprises a copolymerized vinegar. The multilayer film according to the invention, wherein the oxime occupies a copolyester and is dispersed in the heat seal layer. 5. The method as recited in claim 4, wherein the amount of the copolymerized vinegar is in the range of from 0% by weight to 90% by weight of the combined weight of the copolymer and the PLA polymer. 6. The multilayer film of claim 4, wherein the heat seal layer comprises a dispersion phase, and a continuous polymer phase, wherein the adhesion promoter comprises more than 5 〇. One of the phases of wi%, and the PLA polymer constitutes more than 5% by weight of the other of the phases. 7. The multilayer film of claim 1, wherein the 22-200810920 -----j- heat seal layer has a thickness in the range of ^ 〇 μm. The thickness of the heat seal layer in the multilayer of the first item, i, is in the range of 2.0 to 1 G micrometer. And a polymeric group 2, wherein the coaxially oriented polyethylene terephthalate. , a multilayer film, wherein The multilayer film according to claim 1, further comprising an anti-fogging agent dispersed on the surface of the heat-sealing layer which is dispersed in the layer (4) opposite to the wire-free board. A sealed container comprising a container having an opening, wherein the opening is sealed on the film side carrying the heat seal layer with a multilayer film as described in the above application. The sealed container of claim n, wherein the container is formed of a polylactic acid homopolymer or copolymer. 16. A method of preparing a multilayer film comprising the steps of: a) applying a coating liquid to a substrate comprising a polymeric matrix layer, the coating liquid comprising a solvent and a PLA polymer, wherein the coating liquid further comprises an adhesive An accelerator, or the substrate comprising an adhesion promoter in the layer on the surface of the polymeric substrate layer to accept the coating liquid; and 200810920 layer b) removing the solvent to form a heat seal comprising the pLA polymer The method for producing a multilayer film according to the invention of claim 16, wherein the substrate is on the surface of the layer of the f-group, the adhesion promoter, and the coating agent is coated with the coating liquid. The cloth (4) has the method of the invention. The method of claim 17, wherein the adhesion promoter comprises copolymerization g|. The method of claim 19, wherein the method comprises the preparation of the σ-based shell layer of the coating layer comprising the poly-terephthalic acid B-j patent application scope 19 Multilayer ii. vinegar layer '., the household layer of the polymer matrix contains biaxially oriented poly(p-citric acid): square 21 · as claimed in the patent method, wherein the coating (four), the person 7 ^方Λ 1 cloth / night limb contains the adhesion promoter. Wan Tigan, the patent preparation scope f 21 preparation method, wherein the point of you, 隹 ^ 臾 team clothing 1 eve binding The method for preparing a film comprises a copolyester. The method for preparing a multi-layer film according to item 16 of the patent application scope of the patent, wherein the heat-sealing 6 items are used to prepare a multilayer film. Application: =.0 Jobs: Scope ^ Copolymerization S is intended to be heat-sealable. The method of preparing a multi-layer thin fill according to the method of claim 1 of the method of the invention, wherein the PLA polymer Up to 5% by crystallization. 27. The preparation of the multilayer thin method as described in the above-mentioned patent scope, wherein the PLA polymer is amorphous. The method for producing a multilayer film according to claim 16, wherein the PLA polymer is a PLA homopolymer or a copolymer, and the method for preparing a multilayer film according to claim 16 of the patent application. The coating liquid further comprises an anti-fogging agent. 30. The method for preparing a multilayer film according to claim 16 further comprising, after step b), step c): applying an anti-fogging agent to The heat seal layer is a multilayer film prepared by the method as described in claim 16. 32. A coating composition comprising a PLA copolymer, a copolyester, and a solvent. The coating composition of claim 32, wherein the amount of the copolyester is 10 wt/〇 to 90 wt% of the combined turtle weight of the copolyester and the PLA polymer. • 25- 20081092α VII. Designated representative figure: No. 8. If there is a chemical formula in this case, please disclose the chemical formula that best shows the characteristics of the invention: